1. Field of the Invention
This invention relates to a dental syringe of the type having a pre-filled ampule of fluid medication and a double ended hypodermic needle which may be automatically relocated from a distally extended position, at which to inject the fluid medication at a targeted tissue area, to a proximally retracted position, at which the needle is withdrawn within and shielded by the cylinder of the syringe.
2. Prior Art
Dental syringes of the type having a pre-filled ampule of fluid medication and a double ended hypodermic needle are well-known in the art for injecting such medication from the ampule to a targeted tissue area of the patient. For example, reference may be made to U.S. Pat. No. 3,306,290 issued Feb. 28, 1967 to H. S. Weltman. However, at the completion of the injection, the needle is typically locked in an axially extended position projecting outwardly from a distal bore formed through the syringe cylinder.
In some cases, the syringe may be used to treat a patient having a communicable disease. Prior to disposing of the syringe, the hypodermic needle is frequently broken or destroyed to prevent reuse. Dental office workers are especially susceptible to accidental and potentially infectious needle strikes due to the careless handling or breaking of the needle and disposing of the syringe after use. The resulting mini-accident caused by an accidental needle strike typically requires a blood test for such diseases as AIDS and hepatitis. The corresponding cost and inefficiency of testing dental office workers who have received such an inadvertent needle strike result in considerable waste, which may be particularly damaging to a dental facility which is striving for economy.